STRATIGRAPHY AND SEDIMENTATION OF THE SANFRANCISCANA BASIN: A REVIEW This paper presents a stratigraphic and depositional systems review to the Phanerozoic cover of the São Francisco Craton, defined as the Sanfranciscana Basin.The Phanerozoic cover is composed mainly of sedimentary continental rocks and minor explosive volcanic rocks. The stratigraphy and sedimentology of the Phanerozoic successions are summarized as follows: Santa Fé Group (Carboniferous-Permian) -divided into Floresta and Tabuleiro formations. This glaciogenic sequence represents the gondwanan glaciation record in the Sanfranciscana Basin. These sediments are preserved in valleys excavated in the basement and crop out in most of the basin . Areado Group (Early Cretaceous) -constituted by the Abaeté, Quiricó and Três Barras formations, characterized by lateral and vertical interfingerings. The Abaeté Formation was deposited by braided stream and the in southern area by alluvial fans; the Quiricó Formation records a lacustrine sedimentation. and the Três Barras Formation, was deposited in the fluvial, fluviodeltaic and aeolian environments. The Areado Group is thick in southern portion of the basin (200 meters); it is less than 60 meters and discontinous in the central-northern areas. Mata da Corda Group (Late Cretaceous) -composed by the Patos and Capacete formations. The Patos Formation is composed by alkaline volcanic rocks. The Capacete Formation represents the distai epiclastic sediments with important aeolian sand contribution. It is present only in the southern sector of the basin. Urucuia Group (Late Cretaceous) -composed of sandstones, divided into Posse (with Facies l e 2) and Serra das Araras formations, respectively interpreted as dry field dune deposits, braided stream of channelized deposition and braided stream deposited by sheet flows. It is present in the entire basin. In the southern portion of the basin, it is recovered by volcaniclastic sediments, and in the northern area it becomes the most important unit. Chapadão Formation (Quaternary), represents the recent sandy, unconsolidated, covers of talus, residual or alluvium origin. Provenance studies show the following transportation vectors and source areas: Santa Fé Group -NE to S W transport, with source areas in Northern Espinhaço Range and in the Bambuí Group; Areado Group -transport from the adjacent elevated blocks, showing important axial flow; Urucuia Group -transport from NEE to SWW, with sources in the northest São Francisco Craton and the Capacete Formation -showing two directions of transport: volcanic rocks from South to North and aeolian sand from NE to SW.RESUMO Este trabalho apresenta a revisão da estratigrafia e dos sistemas deposicionais da Cobertura Fanerozóica do Craton do São Francisco -Bacia Sanfranciscana. A cobertura sedimentar é constituída essencialmente por rochas depositadas em ambientes continentais e rochas vulcânicas piroclásticas subordinadas, apenas presentes na porção sul da bacia. A estratigrafia das sucessões fanerozóicas inclui as seguintes u...

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ORIGIN AND TECTONIC EVOLUTION OF THE SANFRANCISCANA BASIN This paper presents data about the origin and tectonic evolution of the Phanerozoic cover of the São Francisco Craton, defmed as the Sanfranciscana Basin. The tectonic compartmentation allowed the subdivision in the Abaeté (south portion) and the Urucuia sub-basins (middle-north portion). The stratigraphy and sedimentology of the Phanerozoic successions are as follows: Santa Fé Group (Permo-Carboniferous)-subdivided into the Floresta and Tabuleiro formations. Areado Group (Early Cretaceous) comprising the Abaeté, Quiricó and Três Barras forraations. Mata da Corda Group (Late Cretaceous) composed by the Patos and Capacete formations. Urucuia Group (Late Cretaceous) composed by the Posse and Serra das Araras formations. Chapadão Formation (Cenozoic) represents the sandy, unconsolidated, recent covers of talus, residual or alluvium origin. Paleozoic epyrogenesis characterized the onset of tectonism in the Sanfranciscana Basin. During the Mesozoic the basin has undergone tectonic reactivations fïnishing with neotectonic activity in Cenozoic times. The origin of the basin, as well as its tectonic evolution had been controlled by the São Francisco Craton marginal fold-and-thrust belts (Brasília and Araçuaí belts), by the South Atlantic opening (rift phase) and by transform oceanic fractures (drift phase).

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The Vazante Northern Extension is a continuation of the structurally controlled, hypogene nonsulfide zinc deposit from the Vazante Mine, Minas Gerais, Brazil. The deposit is hosted in Neoproterozoic carbonates of the Serra do Poço Verde Formation located in the Brasília Fold Belt along the western margin of the São Francisco Craton. The Northern Extension deposit is hosted within a shear zone that strikes 200 to 225 and dips 30º-70º NW and is associated with substantial folding that occurred in the same deformation (D 2 ) event and later transcurrent faulting. The shear zone is composed of a tectonic-hydrothermal breccia that can be subdivided into four types:Type 1 Breccia-distally located from the willemite (Zn 2 SiO 4 ) ore, weakly brecciated dolostone with some Fe-carbonate alteration; Type 2 Breccia-Strong Fe-carbonate alteration, intense brecciation; Type 3 Breccia-hematite replacement breccia, usually proximal to the Type 4 Breccia; Type 4 Breccia-willemite ore breccia, containing three generations of hypogene willemite (Zn 2 SiO 4 ) as well as hematite (Fe 2 O 3 ), and franklinite (ZnFe 2 O 4 ). In the southern part of the deposit, late sulfide-rich veinlets are observed cutting the hypogene zinc silicate mineralization, and contain galena, sphalerite, native silver, covellite, and stromeyerite (Cu 1-x Ag 1x S). Geochemical studies conducted on the tectonic-hydrothermal breccia showed a strong regional signature enriched in Ag, Cd, Pb, and Zn. The presence of willemite as opposed to sphalerite and the ubiquity of hematite suggest that the zinc silicate mineralization has formed from the mixing between a low sulfur, acid, oxidizing metalliferous basinal brine similar to the fluids found in MVT deposits with a cooler, more oxidizing, meteoric fluid.iii

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